The invention concerns a transfer film, in particular a hot embossing film, which includes a carrier film and a transfer layer portion having a transparent structure layer, the transfer layer portion being arranged on the carrier film and being detachable from the carrier film, a process for the production of such a transfer film and a multi-layer body.
For protecting documents such as for example identity papers, bank notes or credit cards, it is known to use hot embossing films or laminating films with a carrier which can be pulled off, as security elements. The films include layers with diffractive features, combined with metallic and/or dielectric reflection layers. After the security element has been applied to a substrate there is substantially a smooth reflective surface. Such security elements have optical features which are embedded in the security element.
EP 1 182 054 A2 discloses an embedded structure layer which is provided on both sides with relief structures which by virtue of their co-operation form optical effects. The structure layer is of a layer thickness of up to 200 μm. Arranged on both sides of the film to be embossed are two embossing cylinders which mutually serve as pressure backing cylinders in order to produce an adequate embossing pressure. The great layer thickness means that there is no fear of the two relief structures influencing each other during manufacture. It is preferably provided that a temperature-resistant carrier film, for example of polyester, is coated on both sides with lacquer and the two lacquer layers are embossed.